This invention is discussed with particular reference to, and primarily in terms of, its usefulness as a cleaner/detergent in hospitals for medical instruments and other metal equipment and components, but it is not limited to hospital use or cleaning medical instruments or equipment. As used herein, the term “medical instruments” is intended to mean and include a broad classification of objects, such as surgical instruments (scalpels, biopsy instruments, clamps and the like); endoscopes, proctoscopes, laparoscopes, colonoscopes, and other equipment used for medical or surgical procedures; other metal equipment used in the practice of medicine and/or dentistry as well as hard surfaces encountered in these practices, which require cleaning. In addition, this invention is also intended to include instruments, equipment, hard surfaces and the like in facilities that have similar cleaning requirements, such as, for example, pharmaceutical manufacturing facilities, dairy farms, water recycling, food processing, restaurants, hair salons, cosmetic treatments, veterinary practices, and any other application where cleaning of human or animal blood, protein, lipid soils, or other similar soils are required, and where there is a need for scale control, corrosion inhibition and destaining properties in an applied cleaning composition.
Detergents for use in cleaning medical instruments and other metal equipment (parts, tools, vessels, surfaces) are known in the art. While medical instruments and associated equipment may require sterilization, typically, such instruments and equipment are first cleaned and scrubbed to remove soils, including but not limited to blood, lipid and protein soils, with which they have been coated during use. Instruments/equipment should not be sterilized while they are coated with these soils, since the soil may set as a hardened residue which is difficult to remove later. Soil also presents a barrier to sterilant penetration.
Traditionally, instruments and equipment are manually scrubbed (or rinsed) with, or soaked in, a detergent cleaning solution to remove the bulk of the soil from their surfaces. Soil removal may also be accomplished by placing soiled devices in an automated washer. The volumes of traditional cleaning products used in an instrument processing department within a hospital, or other facility where such cleaning is necessary, are typically very large. In order to achieve high efficiency in processing medical instruments and other equipment, the change out of empty containers to full containers needs to be held to a minimum. As a result, traditional cleaning products are often manufactured as, and sold to, hospitals or other facilities in containers from 5 to 55 gallons. The weight and bulk of these containers poses an ergonomic risk to workers handling the containers. Additionally, the size of the containers occupies valuable space.
One currently available cleaning product addresses the ergonomic and storage space issues associated with bulk cleaning products. The cleaning product is a solid chemistry, which must be diluted in water prior to introduction to the washing or cleaning process. This dry product does not sufficiently protect medical (or other metal) instruments or automated instrument washers from corrosion caused by water and/or contaminants within the water. Nor does it contain sufficient amounts or types of components to prevent the formation of water hardness deposits or scale that result from using hard water (>100 ppm as CaCO3), on medical instruments or other metal equipment, or in automated washers.
Ideally, a useful detergent composition for metal instruments, equipment and hard surfaces should provide for scale control, corrosion inhibition, and destaining of metal surfaces in one product. While most conventional cleaning compositions combine scale control and corrosion inhibition properties, destaining or rust removal is traditionally accomplished using a dedicated destainer that is a separate product. Eliminating the need for an additional destaining product is cost effective both with respect to processing and conserving valuable storage space.
An ideal detergent composition should also provide efficacious cleaning at low use dilutions, i.e., require less volume to clean effectively. Traditional detergents and cleaning chemistries used for cleaning medical instruments and other equipment and hard surfaces are typically diluted in water prior to use at dilutions ranging from about ⅛ oz./gal. to 2 oz./gal. or more. A cleaning concentrate that requires less volume to achieve the same or better cleaning efficacy and provides scale control, corrosion inhibition and destaining properties at low use dilutions is desirable from both cost and ergonomic considerations. Using less of a cleaning concentrate to achieve efficacy, scale control, and corrosion inhibition allows for smaller containers, or less change out of larger containers, and reduces the cost of materials for each cleaning process.
Conventional cleaning compositions achieve scale control and corrosion inhibition by using highly acid or alkaline cleaners containing chelants, sequestrants or other scale and corrosion inhibitors that are not biodegradable. Highly acid or alkaline cleaners are difficult to handle and present environmental, health and safety hazards for users. In addition, highly acidic cleaners, including many separate destainer products that are acidic, can themselves damage metal surfaces, thus making the metal susceptible to further corrosion.
Corrosion inhibition and scale control are easy to achieve and many currently available cleaning products are able to achieve these goals, albeit some products are better than others. Generally, scale control in cleaning concentrates has been and is being achieved by using a chelant for scale inhibition, such as EDTA (ethylene diamine tetra-acetic acid), NTA (nitrilotriacetic acid), phosphates, and phosphonates, which inhibit calcium and magnesium scale deposits, by chemically binding to calcium or magnesium cations, usually in a one-to-one molar ratio, to form a complex, i.e., a chelate. Drew Chemical Corp., Principles of Industrial Water Treatment., 1984, pp. 80-84. In short, one molecule of the chelant combines with one or more ions of calcium, or another metal, to form a new complex. This complex prevents the calcium or magnesium cations from interacting with carbonate anions, thus preventing scale formation. Chelants also prevent metals, such as zinc, copper or iron, from depositing on an instrument or washer surface where they could cause staining or corrosion.
Sequestrants also are used to control scale formation. Sequestrants work in a different manner. One sequestrant molecule may interact with many metal ions and salts. Sequestrants do not prevent the formation of calcium or magnesium carbonate. Rather, they interact with the small calcium and magnesium carbonate particles preventing them from aggregating into a hard scale deposit. The particles repel each other and remain suspended in the water, or form loose aggregates which may settle. These loose aggregates are easily rinsed away and do not form a deposit.
In addition to the specific chelants described above, other compositions have also been used to control calcium carbonate scale and steel corrosion. One example is U.S. Pat. No. 5,647,995, which discloses a method to control scale and corrosion in cooling water using an alkali metal diphosphinate salt that is formed by reacting an acetylenic compound with an alkali metal hypophosphite in the presence of a free radical source. The diphosphinate salt is further reacted to prepare diphosphonate compounds and diphosphinate containing adducts, oligomers, and polymers having control scale and corrosion inhibiting properties.
Another example is U.S. Pat. No. 5,489,666 which discloses a composition for inhibiting the formation and deposition of calcium scales in a circulating aqueous system, such as a cooling water system. The composition used to treat the water is a modified poly-epoxysuccinic acid, which is stated to be effective at conditions of high pH, high calcium concentration and high M-alkalinity, where conventional treatments lose efficacy.
U.S. 2005/0247637 A1 discloses a water treatment for scale control in hard water, which can be used in boilers, or other heating units, hot pipes for commercial, industrial and domestic uses, particularly for drinking water treatment, food service vending and dispensing machines with internal mixing surfaces, boiler or on demand heating elements and similar components. The treatment comprises the combination of metal particulates, e.g., zinc and copper, along with polyphosphates, which is stated to drastically reduce the scale deposition on internal surfaces of high cycle food or beverage dispensing systems with a synergistic effect compared to use of the components alone.
EP 0733073 (WO 95/15984) discloses a carboxymethyl inulin having degrees of substitution (D.S.) ranging from 0.15 to 2.5, which is stated to be useful as an inhibitor of the crystallization of calcium carbonate and is biodegradable. No specific cleaning formulations are disclosed.
Many of the traditional chelants, sequestrants and other scale control agents, including several discussed above, have been the subject of increased regulatory scrutiny due to their impact on the environment. Moreover, conventional concentrated detergents generally require a chelant concentration of 10% or greater in order to be effective when diluted. Typical medical instrument cleaners are diluted to ⅛-2 oz./gal. (in water) resulting in a concentration of 195 ppm to 781 ppm of active chelant/inhibitor in the wash solution. It would be desirable to achieve scale control using a lower concentration of detergent/cleaner to minimize costs, while achieving the same or better results than prior art compositions and having the added advantage of being user and environmentally friendly.
In addition to scale control, control of corrosion in medical instrument and equipment processing is critical to maintaining their safe and effective operation. Many instruments and equipment contain soft metals, such as copper, brass, aluminum and anodized aluminum, which are very susceptible to damage from both the detergents and the water in which they are processed. Typically, neutral cleaning chemistries are used to process these soft metals; however, currently available neutral chemistries, such as STERIS Corporation's Renu-Klenz and NpH Klenz, contain phosphate or phosphonate-based corrosion inhibitors, which are less environmentally friendly. Traditional corrosion chemistries are also diluted to amounts ranging from ⅛ to greater than 2 oz./gal. This level of dilution necessitates large containers of traditional chemistries, which presents an ergonomic risk to instrument reprocessing workers and takes up valuable storage space as well.
Like traditional scale control components, the phosphates and phosphorous containing chemistries used for corrosion inhibition are subject to increasing scrutiny for environmental reasons. As regulations, both international and domestic, become more stringent, the need to replace phosphorous containing chemistries is necessary. Hence, consumer preference and demand for phosphate-free chemistries is expected to increase.
Soft metals are increasingly being used in medical instruments and equipment. As phosphates and phosphate-containing materials are phased out by environmental pressures, maintenance of metal instruments and equipment made from soft metals will be much more difficult, without developing new chemistries to inhibit corrosion. Thus, there is a need for new cleaning compositions that achieve corrosion inhibition with soft metals that is the same or better than that achieved with currently available cleaners and that have a minimal effect on the environment.
In addition to scale and corrosion issues, medical instruments and equipment frequently become stained with various metal deposits and corrosion products. In order to maintain their proper function, halt corrosion, and maintain the appearance of the instruments or equipment, it is necessary to remove the stains or corrosion from the surface of the metal. Conventional destaining and corrosion (rust) removing products are acidic (sometimes highly acidic) and may or may not contain abrasives. For example, U.S. Pat. No. 5,215,676 discloses a chemical composition consisting of a very low pH mixture of hydrochloric and phosphoric acids along with organic ammonium chlorides and organic sulfate, which is stated to be effective for the removal of rust and stains from a variety of surfaces, including metal, concrete, plastic, wood and fiberglass surfaces and non-corrosive to metals. U.S. Pat. No. 4,517,023 discloses a method to remove rust from metal surfaces by applying a coating of an aqueous solution of a copolymer of maleic acid and monomer, which is coated on the metal surface, allowed to dry and is later detached along with the rust from the surface. U.S. 2004/0102344 A1 is a composition for rust removal which comprises a basic compound (such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, and various amines or salts thereof), a water soluble chelating agent, and thiourea dioxide, which gives an alkaline solution when dissolved in aqueous medium and which is stated to have a synergistic effect over any component alone or any two components in combination. The composition is stated to be useful to remove rust occurring on machines and instruments for medical use, such as a dialyzer, water treatment, water pipes, and surroundings.
Acidic rust removers or destainers can damage the surface of metal, if used improperly. For stainless steel, it is expected that staining and/or corrosion will damage the passive layer to some extent. The passive layer of stainless steel is a very thin layer of metal that has a ratio of chromium to iron content that is higher than the bulk metal. The increased chromium content increases the corrosion resistance of the metal. This natural passive layer occurs on stainless steel anytime it is exposed to the air. However, the layer is not very robust and is more susceptible to corrosion than chemically passivated (e.g., using nitric acid, phosphoric acid, citric acid) stainless steel. If an acidic destaining product is used over a larger area, or if it is left in contact with the surface too long, corrosive damage can occur. As such, once the metal is exposed to water, it is more susceptible to corrosion than chemically passivated stainless steel. A similar effect can be seen when products with abrasives are used. Abrasive products scratch the passive layer and create potential sites for future corrosion.
Based on the foregoing, currently available concentrated cleaners present many disadvantages in their use. Many are not biodegradable or user or environmentally friendly, but are subject to strict environmental scrutiny, and present health and safety concerns for workers. Highly acidic and alkaline cleaners present not only safety hazards, but also limit the usable life of medical instruments and other equipment upon which they are used due to their additive corrosive effect. Large volumes are often required to be on site and for efficiency in operations, large containers are often used for detergent supply. These large containers occupy valuable space and present ergonomic risks due to the bulk and weight of the product containers. None of the conventional products achieve both corrosion inhibition and scale control at lower concentrations, and none combine, in one product, destaining ability along with scale control and corrosion inhibition properties.
A new, highly concentrated detergent composition comprising a synergistic combination of corrosion inhibitors, scale control components (chelants, sequestrants), surfactants and a buffer system has been discovered, which surprisingly combines the properties of biodegradability, neutrality, corrosion inhibition, scale control and destaining in one concentrated formulation. The composition also provides effective corrosion inhibition and scale control when used in much lower concentrations ranging from 1/40 oz./gal. to ppm 1/10 oz./gal. than concentrations required by traditional agents. In addition, the composition can, when applied directly to stained metal surfaces, be used to remove stains without damaging the surface of the metal after a contact time of 15 minutes to one hour.
The composition's buffer system provides a neutral pH, which is important to both the physical stability of the composition and its compatibility with metals. The composition also uses a surfactant system which is essential to maintaining the stability of the entire composition and for wetting the surface of the metal.
A primary advantage of the inventive composition is the reduction in costs of processing and ergonomic risk and storage space due to its highly concentrated nature and the low use dilutions required. Even at use dilutions of 1/10 the amount of traditional cleaners, the inventive composition provides efficacious cleaning, while maintaining instrument integrity and controlling water hardness and corrosion at least as well as that achieved with traditional chemistries. The inventive composition eliminates the need for an additional product for destaining metal and is safer and less corrosive when compared to destaining products that are acidic.
Generally, the aqueous, concentrated biodegradable cleaner of the invention comprises the following components:                a) at least one surfactant;        b) at least one scale control component;        c) at least one corrosion inhibitor;        d) a buffer system to maintain a neutral pH; and        e) water.        
Other components may be added as well, such as dyes, perfumes, coupling agents, defoamers, disinfectants, enzymes, solvents and the like.
It is an object of this invention to provide a concentrated cleaning composition for use on medical instruments and equipment and hard surfaces, which avoids the above discussed disadvantages of the conventional compositions and provides a commercial, cost effective alternative.
It is a further object of this invention to provide a concentrated cleaning composition which is safe to handle and use and is environmentally friendly.
It is a further object of this invention to provide a single concentrated cleaning composition for use in cleaning medical instruments, equipment and hard surfaces, without the need for adjunctive cleaners for destaining.
Yet a further object of this invention is to provide in a single concentrated cleaning composition the desired properties of scale control and corrosion inhibition, which are maintained even as the concentrated cleaning composition is diluted.
A further object of this invention is to provide a concentrated cleaning composition, which requires less of the concentrate to be diluted to achieve the above advantages thus reducing costs.
A further object of this invention is to provide a concentrated cleaning composition, which requires less of the concentrate to achieve the same effectiveness as traditional cleaners, thus reducing the need for large volume containers to store the cleaning composition supply and the space needed to store the supply of cleaning concentrate.